Selective ringing telephone system



Oct. 30, 1945. c. G. lMILLER SELEGT'IVE RINGING TELEPHONE SYSTEM Filed Jan. 1l, 1945 3 Sheets-Sheet l wvl/Enron BV C G MILLER A Tron/VE y C. G. MILLER SELECTIVE RINGING TELEPHONE SYSTEM Oct. 30,19745.

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/Nf/ENTOR y C. G M/LLER ATTORNEY 0d. 30, 1945. c. G. MILLER 2,388,071

SELECTIVE RINGING TELEPHONE SYSTEM Filed Jan. 11, 1945 3 sheets-sheet s f aol a//` FIG 3 300 aos l:

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, 4/2 4/ 409V 407 *"H'OU-T E wid /NVE/von' BY C G M/LLER AQ Dcsamayf A TTORNE V Patented Oct. 30, 1945 i l "2,388,071 sELEcrivE IRINGING TELEPHONE SYSTEM Cha/ries G. Miller, Montclair, N. J.,

Bell Telephone Laboratories, Incorporated, New York, N. Y., a'coxporation of .New York Application vJanuary .11, 1945, seran naar;` s claims.. (c1. 1ro- 171i 'This invention relates to telephone systems and has for object to increase the capacity fofffexist ing dial `teleplren'e exchanges with themini-mum of labor and expense. l

`l'larftil'ne restrictions `prevent the manufacture and installation o'f new dial telephone exchanges tcrneet the greatly increased demand for telephone service. Therefore some means is desirable for increasing the number rof Asubscribers who may 'be served equipment already 'in use.

In accordance with the present invention, the capacity of existing dial exchanges of the panel typef to serve `resi'c'ien-tial subscribers may be nearly doubled. To this end, a second residential subscribers line is connected to the terminals of the final selectors, in parallel with the line 4alreadyconnectedtifie'retc. "I'he second lines thus added "are arranged to be cal-led by a different ringing sign-al from that employed in calling the originalline and are assigned the same numeri- L(ral designation but a "different ofce name than that "used 'by the iirst line, the `office codes being usedtocontrol the ringing selection. i

In 'the `panel dial system the ringing equipment "is associated with the incoming selectors, Awhich have access through the-ilna'l selectors with 'all of the called lines of the particular cnice. The selection of a wanted office is performed by district and office selectors under the control of a register by the dial telephone exchange i sender. When a subscriber -dials the code of the office at which a wanted line is located the code is registered in the sender and then is transferred to a decoder, where a route relay is operated individualto the :route to be employed in reaching the the control of the route rewanted oiiice. Under lay, registrations are set up in the sender which serve to control the selections to be made by the `"-district and oilice selectors.

In practicing the present invention in any ofce, certain of the incoming selectors are ar! ranged to provide the proper ringing current for signaling the added second lines which are identiedby the special -oilice code. In those oflices having `access thereto, the route relay correg spending to this special code is cross-connected so that only the modied incoming selectors will be selected.

A clearer understanding of the invention will "be obtained from a consideration of the following `detailed description taken in connection with the accompanying drawings in which:

Fig. A1 shows schematically the switches and control equipment for connecting a calling line with an incoming selector, and twoskeletoniced incoming selectors servi-ng individual lines; Fig. 2 shows two skeletonized `inc-:oming lselec- 'tors serving tw`o-party lines; i

Fig. '3 shows a lfinal selector and two-.individual lnes;and Fig. '4 sho-ws two final selectors and :two two party lines. i

Reference may be made to the following patents for more complete disclosures of the cir?- cuits and equipment Iemployed :in the miesent spe'cica-tion: Patent 1,362,549 to Raymond :and Scully, June 14, T932, for the circhi-ts at innig` in'atingciilce, including the decoder vand .route relays; Aand 'Patent 1,658,829 te C. H. Berryg February 14, `1928, for *the Circuits @i Aa compiete ncoming selector and iinal selecton Y Referring i'irst to Fig.'8, the 'subscribers Islibstation `35| represents the .line originaillylioonne'cted to the terminals 3DS and 3136 of 'the inn-al seiector 300 while `substation 31| represents the second `line connected in parallel with line 3M. Originally 4the ringer '3 02 and condenser 303 were 'connected between the *tip and 'ring condlictm's of the subscribers line 305| VVifhcn line 31 l is connected in parallel with line 3D1, the ringer 302 'is ldisconnected from the tip conductorand conh nected tofground instead; 'Ilie'hewline 3M has its `ringer 312 and condenser 313 corinectedbetween the tip conductor and ground.. l Y

Assuini-ng that the subscriber fat :substation |08 wishes to call line 30| prior to the addition 'of line 3H, the initiation ef the rcallivill cause.v an 'idle' line -nder |10 to *hunt fior andfscze the carb 'ing line |00, Iand an idle isender link` to conneet the line 4iinder |0 with -an idle .senders 1| i2. The subscriber then operates the substation to set 4up a 'registration 'in the sender J1 2 ofV the designation of the wanted line 3M., As soon V,as the oilice `code has been registered, the Asen-der operates decoder connector -||-3 "to seize lan idle decoder JVM *andftransfers -theolle code to `the decoder. The decoder ther-1 translates this icode 'and 4operates a route relayyfer example, H5,

Aindividu/a1 to 'the route to be employed in .reach- .winding of relay merical designation of the line 30| to control selections by the incoming selector |20 and the na-l selector 300 by which the connection is extended to line 30 l.

After the line has been tested and found idle, the control sequence switch of incoming selector |20 is advanced to position |2, in which position, with relay |26 heldoperated by means not shown, the ringing circuit" isf established from ringing source |23, vcontacts ofsequence switch cam |24, winding of ringing relay |25, front contact of relay |26, contacts of cam |21, ring brush |22, ring conductor and brush of nal selector 300, over terminal 306 to the ring side of line 30|, through condenser 303 and ringer 302' tothe trip side of line 30|, terminal 305, tip brush andv conductor of iinal selector 300, brush |2l and right contacts of cam |28 to ground. At the same time a branch of ,this circuit extends through condenser |29 and over cam |30 to the upper right winding of the repeating coil |3| to transmit a ringing tone to the calling line. Relay |25 lcannot operate in response to ringing current, but when the subscriber at substation 30| answers, relay |25 opcrates, releasing relay |26, cutting off the ringing current and advancing the sequence switch to position |4 in which conversation may take place.

When it is desired to increase the capacity of theoiiice by addingthe Aextra lines such as line 3||, a part ofthe incoming selectors are modied as shown in selector |40 by reversing the connections of the ringing source and groundl with the tip and ring brushes of the incoming selector. At the same time, the ringers on the individual Alines are disconnected from the tip conductors of the lines and connected to ground, while the added lines are equipped with ringers connected betweenv the tip conductor of the line and ground. In the ofces having access to the ollce in which the added lines are located, an additional route relay, for example relay ||6 is wired in each decoder to correspond tothe new office name applied to the added lines, the cross-connections being such that the sender will only select the modified incoming selectors in response to the registration of the new oce code. Where only a few trunks terminating in incoming selectors connect a particular originating ofce with the modied terminatnig oce the route relays might be arranged to'mark busy those trunks extending to incoming selectors having the undesired ringing arrangement.

When, after these rearrangements are'made, the subscriber at Vsubstation calls the subscriber at substation 30|, the call proceeds as above described, except that the ringing circuit extends to ground at the ringer instead of to ground at cam |28.V Sincethe open switchhook contacts in line 3|| intervene between the ring conductor and ringer- 3|2 the subscriber on line 3|| will not be disturbed,

On the other hand if the subscriber 4at substation |00 calls the subscriber at substation 3| I, the dialing of the other ofce code will cause the operation of route relay ||6 which in turn will cause the office selector ||8 to pick one ofthe modified incoming selectors, for example selector |40. The operation of incoming selector |40 and the nal selector 300 will be the same as for the call to line 30| .since the numerical designation is the same. When the line terminals have been tested and found idle and the sequence switch is advanced to position |2, the ringing circuit is closed from source |43, contacts of cam |44, |45, contact of relay |46, right contacts of cam |48, tip brush |41, tip conductor `permanent ground as and brush of nal selector 300 to tip terminal 305, ringer 3 |2, condenser 3|3 to ground, signaling the subscriber of line 3| while the subscriber on line 30| is unaware of the call on the other line.

It is apparent that by the means described the capacity of a dial telephone exchange may be largely increased with only a minimum of labor and` substantially no outlay for materials.

AWhere party lines areemployed in` panel type oices,'each party has an' individual number and therefore the line has two or four appearances before final selectors, each appearance being used to signal the corresponding party. The numbers assigned to the stations on one line differ in the hundreds or hundreds and thousands digits and the incoming selector in making the corresponding group selection picks a iinal selector having access to the corresponding appearance of the party line.

' As at present used, a two-party line arranged for semi-selective ringing has the two ringers connected across the line and appears in multiple before two sets of nal selectors which appear. in separate groups before incoming selectors. The

incoming selectors used with such lines are sim- Y ungrounded when the lincoming selector is positioned in accordance with the designations of individual lines or of the one-ring party on party lines.

In order to apply the present invention to such lines, they would be rearranged as shown in Fig. 4. The tip and ring conductors wouldv be reversed at the terminals in the second nal selector group and the ringers between the tip and ground andthe ring and ground respectively, thereby giving the original party line full selective ringing in place of semiselective ringing. The second two-party line, to be connected in parallel with the original4 line would be similarly arranged. f,

At the incoming selectors,jconductor 233 would be disconnectedirom the group commutatgr contact. On a certain` number of selectors, proportioned to the number of second lines toY be served, this conductor would be connected to a v shown at the lower left contact of cam 254. With this arrangement, when a party on the original line, for example substation 40|, iscalled, an incoming selector such as selector22|l is used. When the sequence switch reaches ringing position |2, ringing curvrent from the one-ring source is connectedlover `conductor 2,32, back contacts of relays 236 annd 231, upper contacts ofcam 224, winding of ringing relay 225, front contact of relay 226, right contacts of ycam 221 to brush 222, over the ring conductor and brush of iinalfselectorV 4 09Mto ground through ringers 402 and 4l2. iSince the one-ring signal identliles substation 40|, only the subscriber at that station .will answer. Response at substation'40l operates relay 225, releasing relay 226, cutting off the ringing current and advancing the sequence switch to talking position. To call substation 403, incoming selector 220 would select a final selector like selector 400 which directs the ringing current to 402 and 404 would be connected ample substation 4I3, the special office code will cause the selection of one of the group of special incoming selectors, for example selector 240. After the nnal selections have been completed,

which take place with the incoming selector sequence switch in position 8, that sequence switch is advanced to position I2. In positions 9 to II a circuit is closed from ground over the lower contacts of cam 254, left winding of relay 255 to battery.` Relay 256 operates and locks in a circuit from battery through its right winding anditsiinner right contact, contacts of cam 258, front contact of relay 246 to ground over contacts of cam 259. Relay 256 remains operated in this circuit after its operating circuit is opened at cam 254. With relay 256 operated and the sequence switch in position I2, as soon as the pick-up conductor 253 is grounded, which takes place in the interval between the two-ring signals, relay 251 is `operated over the contact of` relay 256, contacts of cam 254 and ground on conductor 253. Relay 251 locks in parallel with relay 256 and completes the ringing circuit from the two-ring source, over conductor 255, front contact of relay 251, upper contacts of cam 244, winding of relay 245, front contact of relay 248, right contacts of cam 241, brush 242, ring conductor and brush of final selector 46o, terminal 456 to ground through ringers 454 and 4 i 4. Since a two-ring signal identifies substation M3, only the-subscriber at that substation will respond. As in the previous case, the subscribers answer operates relay 245, releasing relay 245 which in turn releases relays 258 and 251.

To call substation 4I I, incoming selector 240 would select a final selector such as selector 405 which directs the ringing current to ringers 402 and 412, the two-ring signal identifying line 4II as called.

It is therefore apparent that in the case of offices employing semi-selective ringing, the addition of second lines in parallel with previously installed two-party lines may be eiected with the use of comparatively little labor and materials. The only change required in the incoming selector is the disconnection of a single conductor in each selector and the connection of that conductor to ground in a portion of them. Likewise, when conditions permit the added lines to be transferred to a new oince, the equipment may be restored to its normal condition with equally little labor.

To apply the invention to four-party lines would be entirely possible, but since it would require more material and labor than for the one and two-party lines, might not prove advisable.

What is claimed is:

1. In a telephone system, a nal selector, sets oi' terminals for said nal selector, called lines,

a plurality of said called lines connected to certain of said sets of terminals, each of the called lines connected to one set of terminals being identiiied by the same numerical designation and by a different ofce code, a plurality of groups 'of incoming selectors having access to said final selector, each group of incoming selectors arranged to signal a different line of the plurality connected to one set of terminals, and means operated in accordance with a, called oince code for selecting an incoming selector in a group arranged to signal the line identied by that code.

2. In a telephone system, nal selectors, sets of terminals for said nal selectors, called lines each having a plurality of substations, a plurality of said called lines connected in parallel to certain of said sets of terminals the called lines connected to`one set of terminals being identified by different cnice codes, the corresponding substations on said lines being identified by the same numerical designations, each substation requiring a different ringing signal, a plurality of groups of incoming selectors having access to said final selectors, each group of incoming selectors equipped with diie'rent arrangements of ringing current, means operated in accordance with the oiice code of the called substation for selecting one of said groups of incoming selectors to determine which line is to be signalled and means operated in accordance with the numerical designation of the called substation to operate the selected incoming selector to determine which substation on the line is to be signalled.

3. In a telephone system, nal selectors, sets of terminals for said final selectors, called lines each having a plurality of substations, a plurality of said called lines connected in parallel to certain of said sets of terminals in a plurality of groups of final selectors, the called lilies connected to one set of terminals being identied by different olnce codes, the corresponding substations on said lines being identified by the same numerical designations, each substation requiring a different ringing signal, a plurality of groups of incoming selectors having access to said final selectors, each group of incoming selectors equipped with diierent arrangements of ringing current, means operated in accordance with the oflice code ofthe called substation for selecting one of said groups of incoming selectors to determine which line is to be signalled and means operated in accordance with the numerical designation of the called substation to operate the selected incoming selector to select a nnal selector in one of said groups to determine which substation on the line is to be signalled.

CHARLES G. MILLER. 

